Permanganate containing whitening compositions and methods of their use

ABSTRACT

In general, the invention provides a fast-acting, whitening composition containing permanganate. Particular alkali-metal or alkaline-earth metal salts of permanganate; hydrogen peroxide; or an alkali or alkaline-earth metal peroxide; and an acid.

This application claims priority to U.S. Ser. No. 60/604,115 which wasfile on Aug. 24, 2004. The entire contents of the aforementionedreference are incorporated herein by reference.

TECHNICAL FIELD

In general, the present invention relates to dental whiteningcompositions. In particular, the invention provides permanganatecontaining compositions that are used as dental whitening agents.

BACKGROUND

White teeth are considered cosmetically desirable. Unfortunately, teethbecome discolored during the normal aging process and when exposed tosubstances such as tobacco, certain chromogens in foods and beverages,such as tea and coffee, and medicinal substances.

The components of teeth that acquire stains are enamel, dentin, andpellicle. Tooth discoloration results from both extrinsic and intrinsicstaining. Extrinsic staining of the tooth surface arises as a result ofthe accumulation of various chromogenic substances (in addition tochromogen precursors, which are initially colorless, but laterchemically convert to chromogens) within the pellicle. This type ofstaining may be reduced by removing the pellicle layer containing theadherent chromogens, such as with mechanical abrasion. As the pelliclelayer reforms in the mouth, extrinsic staining may reoccur and requiresubsequent mechanical removal. Intrinsic staining occurs as a result ofchromogenic substances derived from sources within the tooth, or fromstains derived from external sources that penetrate into the tooth,particularly the enamel layer. Intrinsic staining is not amenable toremoval by mechanical methods of tooth cleaning. This type of stainingmay be reduced by using chemical agents that oxidize or solubilizechromogens in the enamel layer.

Tooth-whitening compositions generally fall into two categories: (1)liquids, powders, gels, or pastes that mechanically or superfluidlyabrade or erode stains located in the pellicle layer; and (2) liquids,gels, or pastes that chemically oxidize the stains in the pellicle andin the enamel or dentin components. Tooth-whitening compositions may beused by professionals in dental offices and by consumers in residentialsettings. The majority of professionals use mechanical abrasion toremove stains and tooth-whitening compositions that oxidate and removedental stains. Current tooth-whitening compositions that utilizeoxidizers are applied to the teeth for a period of time often greaterthan 30 minutes, and sometimes as long as 8 to 12 hours per day for 1 to2 weeks in order to produce noticeable stain reduction. The slow rate ofwhitening is in large part the consequence of formulations that aredeveloped to maintain stability of the oxidizing composition prior touse. These oxidizing compositions typically contain an oxidizing agent,such as hydrogen peroxide or a hydrogen peroxide precursor, e.g.,carbamide peroxide, sodium peroxide, or calcium peroxide, which is mixedwith an anhydrous or low-water content, hygroscopic viscous carriercontaining glycerin and/or propylene glycol and/or polyethylene glycol.Some oxidizing compositions include up to about 38% by weight ofhydrogen peroxide.

Prolonged exposure of teeth to current whitening compositions has anumber adverse effects. These include: 1) sensitizing the tooth to heat,cold, and overly sweet substances possibly due to the use of peroxidesand hygroscopic viscous carriers, 2) irritating mucous membranes withhigh concentrations of peroxide, 3) solubilizing calcium components fromthe enamel layer at pH level less than 5.5 with associated transientdemineralization, 4) penetrating the intact enamel and dentin by thewhitening agents, so as to reach the pulp chamber of a vital tooththereby risking minor penetration of pulpal tissues, and 5) formingreactive species that have been implicated in the formation ofdysplastic cells.

There is a need for whitening teeth while avoiding the adverse effectsusually associated with prolonged exposure to common tooth whiteningcompositions.

SUMMARY OF THE INVENTION

In general, the invention provides a fast-acting, whitening compositioncontaining permanganate.

In one aspect the invention provides a composition including a compoundof the formula R₁(MnO₄)_(n), or mixtures thereof, wherein R₁ is H, analkali-metal, or an alkaline earth metal, and n is 1 when R₁ is H or analkali-metal and 2 when R₁ is an alkaline earth metal and an alkalimetal peroxide, an alkaline earth metal peroxide, or mixtures thereof.

Embodiments of this aspect may include one or more of the following. Thecomposition includes between about 0.005 to about 3.0 percent by weightof the R₁(MnO₄)_(n) compound. The composition includes between about 1.0to about 4.0 percent by weight of the alkali-metal peroxide or thealkaline earth metal peroxide. R₁ is potassium, sodium, or calcium. Thealkali-metal peroxide or an alkaline earth metal peroxide is calciumperoxide or sodium peroxide. The composition further includes athickening agent such as pyrogenic silica, precipitated silica, orsilicate thickening agents.

In another aspect, the invention provides a container including ahousing having a first compartment and a second compartment. The firstcompartment includes a first composition having a compound of theformula R₁(MnO₄)_(n), or mixtures thereof, in which R₁ is H or analkali-metal, or an alkaline earth metal, and n is 1 when R₁ is analkali-metal and 2 when R₁ is an alkaline earth metal. The secondcompartment includes a second composition having an acid.

Embodiments of this aspect of the invention may include one or more ofthe following. The acid is hydrochloric acid, phosphoric acid, aceticacid, sulfuric acid, nitric acid, proprionic acid, maleic acid, orcitric acid. The second composition has a pH less than about 7.5. Thefirst composition further includes an alkali-metal peroxide, an alkalineearth metal peroxide, such as calcium peroxide and sodium peroxide, ormixtures thereof. The first composition includes between about 1.0 toabout 4.0 percent by weight of the alkali-metal peroxide or the alkalineearth metal peroxide. The second composition further comprises ahydrogen peroxide, urea peroxide, an alkali-metal peroxide, an alkalineearth metal peroxide, or mixtures thereof. The second compositionincludes between about 1.0 to about 4.0 percent by weight of hydrogenperoxide, urea peroxide, an alkali-metal peroxide, or an alkaline earthmetal peroxide. The first composition further includes a thickeningagent, such as pyrogenic silica, precipitated silica, or silicatethickening agents. The first composition includes between about 0.005 toabout 3.0 percent by weight of the R₁(MnO₄)_(n) compound. R₁ ispotassium, sodium, or calcium.

In another aspect, the invention provides a container including ahousing including a first compartment and a second compartment. Thefirst compartment includes a first composition having a compound of theformula R₁(MnO₄)_(n), or mixtures thereof, in which R₁ is H, analkali-metal, or an alkaline earth metal, and n is 1 when R₁ is H or analkali-metal and 2 when R₁ is an alkaline earth metal. The secondcompartment includes a second composition having a peroxygen compound,or mixtures thereof, in which the peroxygen compound is hydrogenperoxide, urea peroxide, an alkali-metal peroxide, or an alkaline earthmetal peroxide.

Embodiments of this aspect of the invention may include one or more ofthe following. The second composition includes between about 1.0 toabout 4.0 percent by weight of the peroxygen compound. The alkali-metalperoxide and the alkaline-earth metal peroxide are selected from calciumperoxide, sodium peroxide. The first composition further comprises anacid, such as hydrochloric acid, phosphoric acid, acetic acid, sulfuricacid, nitric acid, proprionic acid, maleic acid, or citric acid. Thefirst composition has a pH between about 4.0 and about 7.5. The firstcomposition further includes a thickening agent, such as pyrogenicsilica, precipitated silica, or silicate thickening agents. The firstcomposition includes between about 0.005 to about 3.0 percent by weightof the R₁(MnO₄)_(n) compound. R₁ is H, potassium, sodium, or calcium.

In another aspect, the invention provides a method of whitening a tooththat includes applying to the tooth a compound of the formulaR₁(MnO₄)_(n), or mixtures thereof, wherein R₁ is H, an alkali-metal, oran alkaline earth metal, and n is 1 when R₁ is H or an alkali-metal and2 when R₁ is an alkaline earth metal; and a peroxygen compound, ormixtures thereof, wherein the peroxygen compound is hydrogen peroxide,urea peroxide, an alkali-metal peroxide, or an alkaline earth metalperoxide. The method may further include the step of applying an acid,such as hydrochloric acid, phosphoric acid, acetic acid, sulfuric acid,nitric acid, proprionic acid, maleic acid, or citric acid, to the tooth.Each of the R₁(MnO₄)_(n) compound, the peroxygen compound, and the acidmay be separately or simultaneously applied to the tooth. For instance,the R₁(MnO₄)_(n) compound and the acid may be simultaneously applied tothe tooth. Alternatively, the peroxygen compound and the acid may besimultaneously applied to the tooth. Still further, the R₁(MnO₄)_(n)compound and the peroxygen compound may be simultaneously applied to thetooth. The peroxygen compound may be applied to the tooth after theR₁(MnO₄)_(n) compound is applied to the tooth. The peroxygen compoundand the acid may be applied as aqueous solutions. The pH of the combinedsolution containing the R₁(MnO₄)_(n) compound, the peroxygen compound,and the acid is between about 4.0 and about 7.5. The peroxygen compoundmay be hydrogen peroxide, urea peroxide, or an alkali-metal peroxide oran alkaline earth metal peroxide, such as such as calcium peroxide orsodium peroxide. R₁ is potassium, sodium, or calcium.

Advantageously, the composition and methods of this invention provide awhitening composition that whitens teeth at a substantially faster ratethan current peroxide based whitening compositions thereby minimizingproblems, such as tooth sensitization, irritation, demineralization,pulpal tissue penetration, and formation or reactive species which mayform dysplastic cells, that result from prolonged exposure to peroxideand/or hygroscopic viscous carriers. Additionally; the whiteningcomposition exhibits a visual signal, such as by turning from apurple-violet color to colorless, when the oxidation process for thatapplication of the whitening composition is complete. Surprisingly, thecomposition and methods of this invention produce whiter teeth eventhough the whitening composition includes the highly chromaticpermanganate.

Other features and advantages of the invention will be apparent from thedescription and the claims which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a dual barreled syringe that may be useful in dispensingcomponents of the whitening composition.

DETAILED DESCRIPTION OF THE INVENTION

The whitening composition of this invention includes three maincomponents, an oxidizing agent, a reducing agent, and an acidifyingagent.

The oxidizing agent includes permanganic acid, permanganate salts, ormixtures thereof. For instance, the oxidizing agent may be permanganicacid, HMnO₄, an alkali-metal salt, or an alkaline-earth metal salt ofpermanganic acid. Examples of suitable oxidizing agents include, but arenot limited to, HMnO₄, KMnO₄, NaMnO₄, and Ca(MnO₄)₂. The oxidizing agentmay be formed as a solution, paste, or gel, and contains between about0.005 to about 3.0 percent by weight (such as between about 0.01 toabout 2.0 percent by weight, between about 0.1 to about 1.0 percent byweight, or between about 0.2 to about 0.6 weight percent) of thepermanganic acid or mixtures thereof. In some embodiments, the oxidizingagent can contain about 30 percent by weight, or less of the permanganicacid or mixtures thereof.

The reducing agent includes hydrogen peroxide or precursors of hydrogenperoxide. Precursors of hydrogen peroxide are compounds that can be usedto form hydrogen peroxide. Examples of suitable reducing agents include,but are not limited to, hydrogen peroxide, urea peroxide, andalkali-metal peroxides, such as sodium peroxide, and alkaline-earthmetal peroxides, such as calcium peroxide. The reducing agent may beformed as a solution, paste, or gel, and contains between about 1.0 toabout 4.0 percent by weight (such as between about 2.0 to about 3.5percent by weight or between about 2.5 to about 3.0 percent by weight)of hydrogen peroxide, precursors of hydrogen peroxide or mixturesthereof. In some embodiments, the reducing agent can contain about 30percent by weight, or less of hydrogen peroxide, precursors of hydrogenperoxide or mixtures thereof.

The acidifying agent includes any inorganic acid, organic acid, ormixtures thereof. Examples of suitable acidifying agents include, butare not limited to, hydrochloric acid, phosphoric acid, acetic acid,sulfuric acid, nitric acid, proprionic acid, maleic acid, and citricacid. The acidifying agent may be formed as a solution, paste, or gel,and contains between about 0.1 to about 2.0 percent by weight (such asbetween about 0.5 to about 1.0 percent by weight) of the acid ormixtures thereof.

When forming a gel or paste of the oxidizing agent, reducing agent, oracidifying agent, a thickening agent is mixed into a permanganatesolution, a hydrogen peroxide solution, a solution of precursors ofhydrogen peroxide, or an acid solution in an amount to achieve thedesired consistency. Examples of thickening agents include, but are notlimited to, pyrogenic silica, precipitated silica, or silicatethickening agents such as magnesium silicate. Other thickening agentsmay be used so long as they do not eliminate the whitening effect of thecomposition such as by oxidatively reducing the permanganate, oxidizingthe hydrogen peroxide or precursors of hydrogen peroxide, orneutralizing the acid.

The whitening composition can be administered by a dental practitionerin a dental office or applied in the home environment by individualsdesiring whiter teeth. The whitening composition is applied to the teethdirectly such as by painting the solutions onto the teeth with a brush,spraying the solutions onto the teeth with one or more syringes, andsoaking the teeth in the solutions, such as with a preformed siliconmouth whitening tray. Silicone mouth whitening trays are available fromHenry Schein Company, located at 135 Duryea Road, Melville, N.Y. 11747.Advantageously, the whitening composition exhibits a visual signal, suchas by turning from a purple-violet color to colorless when the oxidationprocess for that application of the whitening composition is complete.

The three components of the whitening composition, e.g., oxidizingagent, reducing agent, and acidifying agent, may be applied sequentiallyor simultaneously as a single composition. Additionally, as will bedescribed in greater detail below, two of the three components of thewhitening composition may be mixed together before application.

In a sequential application, the oxidizing agent is applied to the teethfor between about 0.2 to about 15 minutes (such as between about 0.2 toabout 5 minutes). In some embodiments, the oxidizing agent is applied tothe teeth for less than about 10 minutes (such as less than about 5minutes). The exact length of application depends upon the concentrationof the permanganic acid and the desired level of whitening. Higherconcentrations require less contact time than lower concentrations.Using highly dilute solutions of oxidizing agent such as (less than0.01% by weight) may require repeated applications of the whiteningcomposition to achieve a desired level of whitening.

After the oxidizing agent has been in contact with the teeth for thedesired amount of time, the reducing agent and the acidifying agent areapplied, in any order, to the teeth to remove excess permanganate andreduction byproducts. Typically, enough acidifying agent is added sothat a mixture of the three components of the whitening composition hasa pH between about 4.0 to about 7.5 (such as between about 4.0 to about5.0). The time required to remove all of the permanganate and reductivebyproducts ranges from between about 30 seconds to about 10 minutes(such as between about 1 to about 5 minutes). At contact times less thanabout 10 minutes, the compounds of the reducing agent, i.e., hydrogenperoxide or precursors of hydrogen peroxide, produce no oxidativewhitening upon visual inspection. The exact length time for applying thereducing agent and the acidifying agent depends upon the concentrationof the permanganate and the concentration of reducing agent.

In a simultaneous application, the oxidizing agent, reducing agent, andacidifying agent are applied simultaneously as a single composition. Forinstance, the three components of the whitening composition are mixedand then applied to the teeth by brush, syringe, or dental tray.Alternatively, each of the three components are separately contained inone of three barrels of a three-barreled syringe and then mixed togetheras they exit the syringe tip. Multiple barreled syringes may be formedby connecting the end of each single syringe to a common tip with, forexample, silicone tubing. FIG. 1 shows an illustration of a dualbarreled syringe that may be useful in dispensing components of thewhitening composition. Multiple barreled syringes are also availablefrom Comprotech, Transcoject, and MixPac. The amount of oxidizing agent,reducing agent, and acidifying agent dispensed by the syringe dependsupon the concentration of permanganate, the hydrogen peroxide orprecursors of hydrogen peroxide, and the acid. In general, themulti-barreled syringe may contain the oxidizing agent, reducing agent,and acidifying agent at any concentration, even above or below thosespecific concentrations listed above. In some embodiments, theconcentrations of the oxidizing agent, reducing agent, and acidifyingagent in the multi-barreled syringe are stoichiometrically adjusted suchthat the solution eluting from the syringe primarily contains HMnO₄. Inother embodiments, the syringe may dispense equal amounts of a oxidizingagent containing 1% by weight of permanganate and of a reducing agentcontaining 3% by weight of hydrogen peroxide or a precursor of hydrogenperoxide. Typically, enough acidifying agent is dispensed from thesyringe so that the mixture of the three components of the whiteningcomposition has a pH between about 4.0 to about 7.5 (such as betweenabout 4.0 to about 5.0).

In other embodiments, two components of the whitening composition aremixed together before being applied to the teeth, e.g., pre-mixed. Forinstance, the oxidizing agent and the acidifying agent are pre-mixed andthen applied to the teeth. After between about 0.2 to about 15 minutes(such as between about 0.2 to about 10 minutes), the reducing agent isapplied to the teeth to remove any residual permanganate and reductionbyproducts. Alternatively, the oxidizing agent is applied to the teethand a pre-mixture of the reducing agent and the acidifying agent isapplied to the teeth to remove residual permanganate and reductionbyproducts. In either scenario, the two components may be pre-mixedimmediately or several days, weeks, or months before application. Thetwo pre-mixed components may be stored in a container such as in onebarrel of a duel-barreled syringe. The other barrel of the syringe couldcontain the remaining component of the whitening composition.

In another embodiment, the oxidizing agent and the reducing agent aremixed together before being applied to the teeth. The acidifying agentis added to the teeth after about 0.2 to about 10 minutes (such asbetween about 0.2 to about 5 minutes). The oxidizing agent and thereducing agent may be mixed immediately before application.Alternatively, when the reducing agent is an alkali metal oralkaline-earth metal peroxide, the oxidizing agent and the reducingagent may be mixed together several days, weeks, or months beforeapplication. The two pre-mixed components may be stored in a containersuch as in one barrel of a duel-barreled syringe. The other barrel ofthe syringe could contain the acidifying agent.

Other embodiments are with the following Examples.

In each of the following examples, the whiteness of a tooth wasdetermined by visual comparison of the tooth with a Vita Shade Guide.Vita Shade Guides are available from VITA ZAHNFABRIK, located in Brea,Calif. The Vita Shade Guides provide a whiteness scale used throughoutthe dental industry. The whiteness of a tooth is determined by visuallycomparing the tooth with the Vita Shade Guide to determine a whitenessgrade. The whiteness shades are given below:

EXAMPLE 1

A 1% by weight solution of potassium permanganate was prepared bydissolving 0.5 grams of potassium permanganate (Sigma-Aldrich,Milwaukee, Wis.) in 49.5 grams of distilled water. The pH of thissolution was determined to be 7.2. A thin layer of this solution waspainted on a severely stained human tooth. The stained tooth whitenesswas darker than any specimen on a Vita Shade Guide.

The painted surface of the tooth had a reddish purple colorcharacteristic of solutions containing permanganate ion. After fiveminutes of treatment, the tooth was washed with a solution of 3% byweight hydrogen peroxide (Sigma-Aldrich, Milwaukee, Wis.) which wasacidified to a pH of 5.0 using citric acid (Sigma-Aldrich, Milwaukee,Wis.). The permanganate color disappeared in a matter of seconds. TheVita Shade Guide rating of the tooth was determined to be A4.

The tooth was re-treated with the potassium permanganate solution for anadditional five minutes, and then washed with the hydrogen peroxidesolution. Again, the permanganate color disappeared almost instantly.The tooth color was determined with a Vita Shade Guide to be D3. Thewhiteness change from A4 to D3 represents a whitening of 5 shades. Aftera third five minute treatment with the potassium permanganate solution,followed by washing with the peroxide solution, the Vita Shade Guiderating was found to be A2. The whiteness change from D3 to A2 representsa whitening of another 5 shades. A forth 5 minute treatment resulted ina Vita Shade Guide rating of A1. The whiteness change from A2 to A1represents a whitening of 3 shades.

EXAMPLE 2

A 0.5% by weight solution of calcium permanganate was prepared by adding0.25 grams of calcium permanganate (made from 0.1 moles CaCl₂ (aq)+0.2K(MnO₄)₂ (aq)) to 49.75 grams of distilled water. The pH of thissolution was found to be 7.1. This solution was painted on a human toothhaving a Vita Shade Guide rating of D3. After five minutes of treatmentthe tooth was washed with the acidified solution of hydrogen peroxideused in Example 1. The Vita Shade Guide rating of the tooth wasdetermined to be C1. The whiteness change from D3 to C1 represents awhitening of 4 shades. After 5 minutes of additional treatment, followedby washing with the hydrogen peroxide solution, the tooth had a VitaShade Guide rating of D2. The whiteness change from C1 to D2 representsa whitening of 3 shades.

EXAMPLE 3

Example 1 was repeated by treating a human tooth having a Vita ShadeGuide rating of A4 with the 1% by weight potassium permanganate solutionfrom Example 1. A 3.0% solution of hydrogen peroxide (Sigma-Aldrich,Milwaukee, Wis.) acidified to a pH of 5.0 with phosphoric acid(Sigma-Aldrich, Milwaukee, Wis.) was used to wash the tooth. Aftertwelve minutes of treatment with the potassium permanganate solutionfrom Example 1 followed by the acidified peroxide wash, the Vita ShadeGuide rating of the tooth was found to be A2. The whiteness change fromA4 to A2 represents a whitening of 10 shades The tooth was retreated forfive minutes with the potassium permanganate solution from Example 1followed by the acidified peroxide wash. The final Vita Shade Guiderating was found to be Al. The whiteness change from A2 to D1 representsa whitening of 3 shades.

EXAMPLE 4

An aqueous gel containing 1% by weight of potassium permanganate wasprepared by adding 0.5 grams of potassium permanganate (Sigma-Aldrich,Milwaukee, Wis.) and 5.0 grams of CAB-O-SIL L-90 (Cabot Corporation,Tuscola II, 61953) to 44.5 grams of distilled water. A 3.0% by weightsolution of hydrogen peroxide (Sigma-Aldrich, Milwaukee, Wis.),acidified to a pH of 5.0 with hydrochloric acid (Sigma-Aldrich,Milwaukee, Wis.) was gelled by adding 6 grams of CAB-O-SIL L-90 to 44.0grams of aqueous solution.

The potassium permanganate gel was spread on the surface of a humantooth having a discoloring darker than specimens on the Vita ShadeGuide. The surface color of the tooth was reddish-violet. After 6minutes of treatment with the potassium permanganate gel, the hydrogenperoxide gel was spread on the tooth. After about two minutes, the colorof the tooth was a light yellow. The tooth was washed with distilledwater and the tooth color was rated with the Vita Shade Guide as B4,representing a change in whiteness of at least 4 shades. The tooth wasre-treated in the same manner for an additional 8 minutes. The VitaShade Guide color was determined to be C2. The whiteness change from B4to C2 represents a whitening of 6 shades. After an additional 4 minutesof treatment, the Vita Shade Guide rating of the tooth was found to bebetween A1 and B1, representing a change in whiteness of at least 5shades.

EXAMPLE 5

Solution A). A 1% by weight solution of potassium permanganate wasprepared by dissolving 0.5 grams of potassium permanganate(Sigma-Aldrich, Milwaukee, Wis.) in 49.5 grams of distilled water.Solution B), a 1.4% by weight of calcium peroxide, was prepared byadding 0.7 grams of calcium peroxide (Sigma-Aldrich, Milwaukee, Wis.) to49.3 grams of distilled water. Solution C) was prepared by mixing 20grams of Solution A to 20 grams of Solution B. Solution D), a 1% byweight solution of citric acid (Sigma-Aldrich, Milwaukee, Wis.) wasprepared by adding 1 gram of citric acid to 99 grams of distilled water.

A human tooth having a Vita Shade Guide shade of D4 was placed in a 50cc plastic vial. 6 cc's of Solution C was added to the vial containingthe tooth using a plastic hypodermic syringe. 6 cc's of Solution D) wasimmediately injected into the vial, and the contents were swirled toachieve mixing. The pH of the solution containing the tooth was found tobe 4.5. After 5 minutes, the tooth was removed from the vial, rinsedwith distilled water. The color of the tooth was determined with theVita Shade Guide to be C2, representing a change in whiteness of 1grade.

The tooth was placed back in the vial containing the mixture ofSolutions C) and D). After an additional five minutes, the tooth wasremoved and rinsed with distilled water. Its Vita Shade Guide readingwas found to be D2, an improvement of four shades.

The color of the mixture of Solution C) and D) was light yellow after 12minutes. The tooth was added back to this mixture, and after anadditional 5 minutes, it was removed and again rinsed with distilledwater. The Vita Shade Guide evaluation was found to be D2, and thesolution in which it had been treated was clear. An additional fiveminutes of treatment produced no further reduction in shade.

This example demonstrates the tooth-whitening efficacy of compositionscontaining alkali-metal salts of permanganic acid.

EXAMPLE 6

Experiment 1 was repeated using a tooth having a Vita Shade Guide ratingof A3.5. After five minutes of treatment, its Vita Shade Guide ratingwas C1, corresponding to an improvement of 6 shades. Further treatmentof the tooth for an additional 5 minutes resulted in a Vita Shade Guiderating of between shade D2 and A2, an additional change of 1 shade. Thetreating solution was completely clear after 20 minutes.

EXAMPLE 7

The teeth used in Experiments 1 and 2 were re-treated using the exactmethod used in Experiment 1. After five minutes of treatment, the shadeof the tooth used in Experiment 1 was determined to be B2, a furtherimprovement of 1 shade. The shade of the tooth used in Experiment 2 wasalso determined to be B2 corresponding in change in whiteness of anadditional 2 shades. After an additional five minutes of treatment, thetooth used in Experiment 1 was found to have a Vita Shade Guide shade ofA1, for an additional improvement of one shade. The solution used totreat this tooth was a very light yellow after this treatment. Withinone hour the solution was water-white and crystal clear.

An additional five minutes of treatment resulted in no furtherimprovement in shade of the tooth used in Experiment 2. Again, withinone hour the treating solution was water-white and crystal clear.

These experiments demonstrate the whitening efficacy of multipletreatments of tooth-whitening compositions containing alkali-metal saltsof permanganic acid.

EXAMPLE 8

A human tooth having a Vita Shade Guide rating of D4 was immersed in 6cc's of calcium peroxide (made as described in example 2) solutionhaving the composition of Solution B above. 6 cc's of 1% citric acidsolution prepared by adding 0.5 grams of citric acid (Sigma-Aldrich,Milwaukee, Wis.) in 49.5 grams of distilled water were added to themixture. The pH of the acidified solutions was determined to be 4.3.

After five minutes immersion, the tooth was removed from the solution,rinsed with distilled water. The Vita Shade Guide reading was determinedand found to be D4.

The tooth was re-immersed in the in the acidified Solution B. After 10minutes, the tooth was removed and found to have a Vita Shade Guidereading of D4.

The tooth was re-immersed in the acidified Solution B. After 20 minutes,the tooth was removed and tested for shade. The Vita Shade Guide ratingwas again D4.

The tooth was again re-immersed in the acidified Solution B. After onehour, the Vita Shade Guide rating remained at D4.

This experiment demonstrates that acidified solutions of calciumperoxide, without the necessary alkali-metal salts of permanganic acid,exhibit no visible efficacy in reducing the color of stained teeth.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

1-50. (canceled)
 51. A method of whitening a tooth comprising: applyingto the tooth an oxidizing agent comprising a compound of the formulaR₁(MnO₄)_(n), or mixtures thereof, wherein R₁ is H, an alkali-metal, oran alkaline earth metal, and n is 1 when R₁ is H or an alkali-metal and2 when R₁ is an alkaline earth metal; and a reducing agent comprising aperoxygen compound, or mixtures thereof, wherein the peroxygen compoundis hydrogen peroxide, urea peroxide, an alkali-metal peroxide, or analkaline earth metal peroxide; wherein the oxidizing agent is applied tothe tooth for between about 0.2 to about 15 minutes followed by theapplication of the reducing agent, and the oxidizing agent reacts withthe reducing agent on the tooth's surface to whiten the color of thetooth by at least one shade according to the Vita Shade Guide.
 52. Themethod of claim 51, wherein the oxidizing agent further comprisesbetween about 0.005 to about 3.0 percent by weight of the compound ofthe formula R₁(MnO₄)_(n).
 53. The method of claim 51, wherein thereducing agent further comprises between about 1 to about 4 percent byweight of the peroxygen compound.
 54. The method of claim 51, whereinthe oxidizing agent, the reducing agent, or both further comprises anacid.
 55. The method of claim 54, wherein the acid is selected fromhydrochloric acid, phosphoric acid, acetic acid, sulfuric acid, nitricacid, proprionic acid, maleic acid, or citric acid.
 56. The method ofclaim 55, wherein the concentration of the acid in the oxidizing agent,the reducing agent, or both is sufficient to adjust the pH of themixture of oxidizing agent, the reducing agent, and the acid to betweenabout 4.0 and about 7.5.
 57. The method of claim 56, wherein thereducing agent further comprises the acid.
 58. The method of claim 51,wherein the oxidizing agent, the reducing agent, or both furthercomprise a thickening agent.
 59. The method of claim 58, wherein thethickening agent comprises pyrogenic silica, precipitated silica,magnesium silicate, or any combination thereof.
 60. The method of claim51, wherein the oxidizing agent is housed separately from the reducingagent prior to the application of the oxidizing agent and the reducingagent to the tooth.